As an operating device mounted on a recent vehicle, that uses power generated by a motor is widely used in order to reduce operation force at the time of driving operation of a driver. For example, in an electric power steering device disclosed in Patent Literature 1, a decelerating mechanism and a pinion shaft of the motor are attached to an output shaft which outputs steering force to a steering wheel operated by the driver to a side of a rack-and-pinion transmission mechanism so as to be integrally rotatable. According to this, when the driver steers the steering wheel, the motor is driven and rotational torque transmitted from the output shaft to the side of the rack-and-pinion transmission mechanism is increased, so that a burden of the driver in the steering is reduced.